This invention relates to an universal joint and, more particularly, to an universal joint which has an excellent responsibility to change in an inclination angle of coupled shafts and which is suitable to transmit a large torque.
A conventional universal joint using driving pins is disclosed in Japanese Patent Laid-Open No. 61-206826/1986, wherein three driving pins are arranged on a circle with an equiangular distance therebetween, open each the driving pin having a spherical portion formed at an end thereof and connected to one end of a shaft so as to be rotatable and swingable, and the other end of each driving pin being axially slidably connected to another shaft through a spherical bearing.
In the above universal joint, radial displacement of the driving pins corresponding to change in inclination angle of the shaft was not taken into consideration. Therefore, when the shafts rotate with inclination angle between the axes of the shafts stable rotation can not be obtained by such a joint. Further, the conventional universal joint has a mechanism wherein torque is transmitted by the action of levers with each the spherical bearing as a fulcrum, namely, when torque of the driving shaft is applied on the spherical portion of the driving pin, the spherical bearing functions as the fulcrum, and a tip portion of driving pin at other end thereof drives the driven shaft to rotate, so that a driving force concentrates on the tip portion of each driving pin and the joint is not suitable to transmit a large torque.